Refrigerating capacity control device, a testing apparatus and a refrigerating control method using the device

ABSTRACT

This invention hereof discloses a refrigerating capacity control device, a test apparatus and a refrigerating control method using the device. The refrigerating capacity control device comprises a compressor ( 2 ), a condenser ( 5 ), an evaporator ( 7 ), a controller ( 1 ), a pressure regulating valve ( 4 ), a throttling device ( 6 ), a control panel ( 13 ) for driving a hot-gas valve, and a hot-gas valve ( 11 ). The controller is connected with the hot-gas valve ( 11 ) through the control panel ( 13 ) for driving a hot-gas valve; the pressure regulating valve ( 1 ) is disposed between an outlet of the compressor ( 2 ) and an inlet of the condenser ( 5 ) that are arranged in the refrigerating device; the throttling device ( 6 ) is disposed between an outlet of the condenser ( 5 ) and an inlet of the evaporator ( 7 ); one-end of the hot-gas valve ( 11 ) is disposed on a pipeline between the outlet of the compressor ( 2 ) and the front end of the pressure regulating valve ( 4 ), and the other end thereof is disposed on a pipeline that is between the throttling device ( 6 ) and an inlet of the evaporator ( 7 ).

FIELD OF THE INVENTION

This invention is related to a hot-gas refrigerating capacity control device for accurate control of refrigerating capacity in climatic and environmental testing equipment. Particularly, this invention makes it possible for the refrigerating system to operate and maintain a temperature close to or higher than ambient temperature with less or no accessory heating. It can decrease the power consumption from additional heating, increase energy efficiency ratio and even eliminate the use of a heater. The control device features in simpler structure and lower energy consumption. It can be used as an important means of accurate temperature control for climatic and environmental testing equipment. Moreover, the invention also relates to a testing apparatus incorporating the refrigerating capacity control device and a control method used in such control device.

BACKGROUND OF THE INVENTION

Climatic and environmental testing equipment (such as liquid baths and circulators, climatic and environmental testing chambers and refrigerated incubators etc.) has wide application in manufacturing, scientific research for laboratory and process control, in the fields of pharmaceuticals, medical sanitary, biotechnology, agriculture and forestry, electronics and electrics, metrological inspection and verification, civil engineering and petroleum chemicals etc.

The refrigerating device is one of the important indispensable assemblies for climatic and environmental testing equipment. Refrigerating device and technologies are applied in all testing equipment requiring low temperature (below ambient temperature) or heat withdrawal during normal operation. For the requirements of accurate temperature control and the features of small quantity and diversities for application, the refrigerating capacity and energy saving control of climatic and environmental testing equipment have been an important subject but are neglected for long times. The temperature control for almost all climatic and environmental testing equipment incorporating refrigerating device are based on conventional technology of continuous refrigeration and additional counter heating, resulting in increased electric current drawing and substantial energy waste.

According to FIG. 1, a traditional refrigerating device fundamentally comprises a compressor, a condenser, a throttling device and an evaporator. The use of capillary tube, thermal expansion valve and electronic expansion valve as a throttling device and an indispensable important part for the refrigerating device, is a sign evidencing the development course, from simple to automatic control, of refrigerating technology. In accurate control of refrigerating capacity, the development and application of electronic expansion valve has been playing a more and more important role.

For refrigerating capacity control, the modern technologies of inverter compressor, electronic expansion valve and heat pump have been extensively used in household or commercial electrical appliances. The inverter compressor and electronic expansion valve as a whole are usually incorporated in the refrigerating device for refrigerating capacity control. The success in the application of such technology is based on specific inverter compressor, sophisticated sensing and calculation of the superheat. Without extensive marketing survey, sufficient budget for engineering and manufacturing investment, it is difficult to apply this technology in general purpose appliance and equipment. Compared to traditional resistance electric heating, the heat pump technology, incorporated with a 4-way valve for switchover of the condenser and evaporator for heating and refrigerating, has the advantage of extremely higher energy efficiency ratio and energy saving property. Nevertheless, the refrigerating capacity control needs to be depended on the technologies of inverter compressor and electronic expansion valve.

Currently, the electronic expansion valve has been extensively used in the fields of household electrical appliances and commercial refrigeration. It is specifically used as a throttling device to match the system requirements of inverter compressor refrigeration. Its key function is to control the degree of superheat at the evaporator outlet. The electronic expansion valve is normally located between the condenser outlet and the evaporator inlet. Based on requirement for the degree of superheat at the evaporator outlet, the electronic expansion valve is regulated to open, close or maintain at certain degree of opening to respond changing temperature and heat load for possible maximum refrigerating capacity. Because of the specific purpose of superheat control, the electronic expansion valve as throttling device has the limitation for optimized refrigerating capacity and precise temperature control. To acquire an accurate superheat value, it is required that evaporating temperatures and/or refrigerant pressures at beginning and ending portions of the evaporator be measured. Therefore, the degree of complexity and reliability for the control circuit and software algorithm becomes critical to the success of the system. Without optimistic prospect of industrialization and sufficient budget for engineering and manufacturing investment for mass production, it is difficult to afford the expensive cost for a sophisticated and reliable system. In the mean time, the application temperature range of traditional electronic expansion valve is limited between ambient temperature and −40° C., while the requirements for application in climatic and environmental testing equipment are extended down to −90° C. and up to +300° C. With the status of small quantity and diversity in application, it is difficult to apply the electronic expansion valve in climatic and environmental testing equipment for precise temperature and refrigerating capacity control, in the traditional way as in household and commercial appliances.

The hot-gas bypassing refrigeration is characterized in an additional hot gas bypassing channel into a traditional refrigerating device to achieve simple normal cooling and hot-gas bypassing heating. Its basic working principle is to close the hot-gas valve for maximum refrigerating capacity when cooling is expected. When the refrigerating capacity needs to be decreased or heating is desired, the hot-gas valve is opened and the hot refrigerant vapor from the discharge outlet of the compressor is directly bypassed into the evaporator without cooled by the condenser. As a result, the refrigerating capacity is restrained, the cooling is limited and even heating is possible. When constant temperature is required, the hot-gas valve is opened and closed at certain frequency to achieve regulation of refrigerating capacity and constant temperature. Although it is popular knowledge, the current hot-gas bypassing technology has the disadvantages of:

(1) Due to the restrain from the service life of a solenoid valve, the operation interval of the hot gas bypassing should be limited to certain extent. As a result, the control precision of refrigerating capacity is also limited;

(2) With the solenoid valve remaining opened for a long time under continuous heating condition, the discharge pressure of the compressor will decrease gradually. As a result, the refrigerating device based on hot-gas bypassing can only achieve limited heating or even no heating. It is actually difficult to maintain an operating temperature close to or higher than ambient;

(3) With the function and operation of a solenoid valve, it emits unfavorable noise including that of valve operation and that of hot-gas flow; and

(4) The stress of pressure impact resulting from operating of the solenoid valve creates additional fatigue and reduces the service life of related refrigerating parts or components, including the solenoid valve itself.

SUMMARY OF THE INVENTION

This invention is intended to provide:

-   a refrigerating capacity control device to address the technical     difficulties in the control of refrigerating capacity, the     regulation of temperature and its excessive energy consuming in a     refrigerated climatic and environmental testing equipment;

a testing apparatus incorporating the refrigerating capacity control device; and

a control method used in the refrigerating capacity control device.

The technical solution of the invention to address relevant technical difficulties is:

A refrigerating capacity control device comprises a controller, a pressure regulating valve, a throttling device, a refrigerating device, a control panel for driving a hot-gas valve, and a hot-gas valve. The controller is connected to the hot-gas valve through the control panel for driving a hot-gas valve; the pressure regulating valve is located between a discharge outlet of the compressor of the refrigerating device and an inlet of the condenser; the throttling device is installed between an outlet of the condenser of the refrigerating device and an inlet of the evaporator; the hot-gas valve, having one-end installed on a pipeline between the discharge outlet of the compressor and a front end of the pressure regulating valve, and another end installed on a pipeline between a location downstream from the throttling device and the inlet of the evaporator.

The refrigerating capacity control device, wherein the throttling device is a thermal expansion valve.

The refrigerating capacity control device, wherein the throttling device is a capillary tube.

The refrigerating capacity control device, wherein the throttling device is an electronic expansion valve.

The refrigerating capacity control device, wherein the hot-gas valve is a continuously variable, electrically operated valve or an on/off solenoid valve.

The refrigerating capacity control device, wherein the refrigerating device comprises a compressor, a condenser and an evaporator connected sequentially by pipelines.

A testing apparatus incorporating the refrigerating capacity control device, the testing apparatus comprising:

-   -   a refrigerating capacity control device, a chamber or bath         requiring temperature control and a temperature sensor;     -   an evaporator of the refrigerating capacity control device and         the temperature sensor are installed within the chamber or bath         requiring temperature control;     -   the temperature sensor is connected to a controller of the         refrigerating capacity control device.

A refrigerating capacity control method comprising:

-   -   installing a pressure regulating valve between the compressor         and condenser of a traditional refrigerating device; installing         one-end of a hot-gas valve on a pipeline between an discharge         outlet of the compressor and a front end of the pressure         regulating valve, and another end of the hot-gas valve on a         pipeline between a location downstream from the throttling         device and an inlet of the evaporator;     -   connecting the hot-gas valve to the controller by using a         control panel for driving a hot-gas valve;     -   installing a throttling device between an outlet of the         condenser of the refrigerating device and the inlet of the         evaporator;     -   wherein the pressure regulating valve is used to maintain a         stable discharge pressure and a hot-gas temperature to avoid the         discharge pressure being affected by the switching-on or         switching-off of the hot-gas valve;     -   wherein the throttling device is used to independently control         the evaporating temperature and degree of superheat; and     -   wherein the hot-gas valve releases directly the hot vapor from         the discharge outlet of the compressor according to its opening         setting or frequency. the pressure regulating valve reduces the         output of a refrigerating system by restricting the refrigerant         entering the condenser, and thereby heating and refrigerating         capacity is effectively controlled and the temperature is         precisely maintained at a set value.

The hot-gas valve is a continuously variable, electrically operated valve or an on/off solenoid valve.

This invention has the beneficial effects in that traditional electronic valve or solenoid valve are used as hot-gas bypassing valve, combined with a traditional throttling device to constitute a refrigerating device. As a result, the accurate control for refrigerating capacity between 300W-15 kW or higher, and precise temperature control for refrigerating device operating between −90˜+20° C., are readily achieved, even when the refrigerating device is expected to work under operating temperature lower than −30° C. and, even when the orifice of the hot-gas valve is relatively bigger. As one of the most critical control assemblies of the refrigerating device for climatic and environmental testing equipment, it eliminates the defects that the refrigerating capacity cannot be controlled continuously with traditional thermal expansion valve or capillary tube, and that the electronic expansion valves available for commercial appliances are featured with excessive refrigerating capacity and lower control precision.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structural diagram of a traditional refrigerating device.

FIG. 2 shows the structural diagram of a testing apparatus utilizing the refrigerating capacity control device of the invention, wherein

1. Controller; 2. Compressor; 3. Condenser fan; 4. Pressure regulating device; 5. Condenser; 6. Throttling device; 7. Evaporator; 8. Circulating fan or pump; 9. Chamber or bath requiring temperature control; 10. Temperature sensor; 11. Electronic expansion valve; 12. Refrigerating pipeline; 13. The control panel for driving an electronic expansion valve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Operation of the refrigerating capacity control device can be understood by reference first to a traditional refrigerating device as shown in FIG. 1 and then by reference to the current invention as shown in FIG. 2. A refrigerating capacity control device comprises a controller (1), a compressor (2), a condenser fan (3) , a pressure regulating valve (4), a condenser (5) , a throttling device (6), an evaporator (7), circulating fan or pump (8), chamber or bath (9) requiring temperature control, temperature sensor (10), an electronic expansion valve for hot-gas bypassing (11), refrigerating pipelines (12) and a control panel (13) for driving an electronic expansion valve. Wherein, the compressor (2), the condenser (5), the throttling device (6), and the evaporator (7) connected sequentially by refrigerating pipeline (12), condenser fan (3) for the condenser (5) , chamber or bath (9) requiring temperature control and circulating fan or pump (8) for forced convection are parts for a traditional refrigerating device. Wherein, the electronic expansion valve (11) functions as the hot-gas bypassing valve (11), connected in parallel, having one-end installed on a pipeline between the discharge outlet of the compressor (2) and a front end of the pressure regulating valve (4), and another end installed on a pipeline between a location downstream from the throttling device (6) and the inlet of the evaporator (7).

The control panel (13) for driving an electronic expansion valve accepts driving signals such as voltage or current from the controller (1) and directly regulates the opening, closing and opening degree of the hot-gas bypassing valve (11). The controller (1) is connected to the compressor (2), temperature sensor (10), condenser fan (3), circulating fan or pump (8) and control panel (13) for driving an electronic expansion valve for input and output control. The temperature sensor (10) and evaporator (7) are installed within the chamber or bath (9) requiring temperature control for heating, cooling and maintaining the temperature.

The controller (1) can start or stop the operation of compressor (2), condenser fan (3) and circulating fan or pump (8). With the temperature sensor (10), the controller (1) can detect the temperature of the air or liquid in the chamber or bath (9) requiring temperature control. Compared to the set temperature of the controller (1), in case of a higher actual temperature, the electronic expansion valve (11) tends to be closed, while in case of lower actual temperature, the electronic expansion valve (11) tends to be opened. With the actual temperature becomes stabilized, the opening degree of the electronic expansion valve (11) tends to be constant.

The compressor (2), condenser (5), throttling device (6) and evaporator (7) are fundamental components of a traditional refrigerating device. The function of the compressor (2) is to suck the refrigerant vapor of low pressure/normal temperature from the evaporator (7), and pressurize it to deliver high pressure/high temperature vapor. The models of the compressor (2) include types of reciprocating, rotary, scroll and screw. The function of the condenser (5) is to condense high pressure/high temperature refrigerant vapor, as cooled by condenser fan (3) or other liquid coolant, to become high pressure/normal temperature refrigerant liquid. The condenser (5) can be any type of fin tube, sleeve, shell tube, plate and etc. The function of the throttling device (6) is to lower the pressure of the refrigerant liquid to produce low temperature when the refrigerant boils and evaporates with its pressure dropping. In the practical application, the throttling device (6) can be capillary tube, thermal expansion valve, electronic expansion valve or any available conventional expansion device. The function of the evaporator (7) is to provide a space where the liquid refrigerant boils and evaporates. During the evaporating or boiling process of the liquid refrigerant, the evaporator (7) keeps absorbing the heat from ambient, presenting cooling effect of the refrigeration. The critical aspect of the design for the refrigerating system is that liquid refrigerant keeps evaporating completely within the evaporator (7) to the extent for maximum superheat of 5° C. As a result, when the refrigerant vapor leaves the evaporator (7), its temperature is close to the operating temperature of the chamber or bath (9) requiring temperature control or the ambient temperature where the equipment is installed.

The pressure regulating valve (4) is a special automatic control device to maintain discharge temperature of the compressor (2). The pressure regulating valve (4) is not an essential component for traditional refrigerating device, but is a specific component particular to this invention. The mechanism of pressure regulating valve (4) is, with the increase of the discharge pressure, it tends to open allowing more refrigerant flow. In other words, when the pressure reaches the set value, the pressure regulating valve (4) starts to open. The operation of the pressure regulating valve (4) is dependent on the discharge pressure of the compressor (2), and has nothing to do with the pressure at the outlet of pressure regulating valve (4) or the pressure in the condenser (5). In this case, the affection on the discharge pressure resulting from operation of the electronic expansion valve (11) can be minimized. As a result, stable discharge pressure and hot-gas bypassing temperature can be guaranteed. Even when the electronic expansion valve (11) keeps opening continuously, the constant discharge pressure can guarantee stable heat source to ensure sufficient heating temperature and precise temperature control. In other words, without the pressure regulating valve (4), it is not possible for the refrigerating device to achieve energy regulation as expected. When the temperature in the chamber or bath (9) requiring temperature control increases, the electronic expansion valve (11) will be closed to achieve normal refrigeration. When the temperature in the chamber or bath (9) requiring temperature control becomes lower, the electronic expansion valve (11) will be opened. Without the pressure regulating valve (4), the discharge pressure will decrease gradually with the electronic expansion valve (11) opened and the heating in progress. Although the electronic expansion valve (11) is kept opened for heating, the heating temperature is not high enough and the heating energy is limited. At the same time, the refrigeration is still possible through the normal function of the condenser (5) and throttling device (6). As a result, under particular conditions, the heating by hot-gas bypassing cannot be expected, not to mention the regulation of the refrigerating capacity. In addition, the incorporation of the pressure regulating valve (4) can increase the heating temperature from the electronic expansion valve (11) and hot-gas bypassing, and limit the refrigerating capacity of the throttling device (6) as well. The increased temperature and limited cooling are the critical aspects for the regulation of refrigerating capacity and hot-gas bypassing heating.

The chamber or bath (9) requiring temperature control is the most popular component associated with the refrigerating device in climatic and environmental testing equipment. In order to meet the requirements of temperature range and operating conditions of climatic and environmental testing equipment, the chamber or bath (9) requiring temperature control is usually composed of interior chamber or bath tank, enclosure and insulating materials. For easy operation and access, the chamber and bath (9) is also equipped with a door or cover. In case the operating temperature is far beyond the ambient temperature, the door or cover must also be insulated, together with the sealing gasket or cushion.

The temperature sensor (10) is used to detect the temperature of the air or liquid in the chamber or bath (9) requiring temperature control. The position of temperature sensor (10) and the operation of circulating fan or pump (8) are important and will severely affect the truth of sensed temperature, and as a result affect the operation of the electronic expansion valve (11) for hot-gas bypassing.

The electronic expansion valve (11) and control panel (13) for driving an electronic expansion valve are specific components particular to the preferred embodiment of this invention. The control panel (13) for driving an electronic expansion valve is an automatic assembly with its opening, closing and degree of opening regulated by and proportional to the input of voltage or current. The control panel (13) for driving an electronic expansion valve accepts driving signals such as voltage or current from the controller (1) and directly regulates the opening, closing and opening degree of the hot-gas bypassing valve (11). The output of the control panel (13) shall be compatible to the driving required by the electronic expansion valve (11). Usually, when the control panel (13) receives an input voltage of 0V or current of 4 mA, the electronic expansion valve (11) shall be fully closed. While the control panel (13) receives an input voltage of 5V or current of 20 mA, the electronic expansion valve (11) shall be fully opened. When the input signal ranges between the maximum and minimum values, the position or degree of the opening for the electronic expansion valve (11) shall be linearly proportional to the input level. Therefore, in case the detected temperature is higher and the output voltage or current of the controller (1) becomes smaller, the opening degree of the electronic expansion valve (11) will become smaller. As a result, the refrigerating capacity is increased and the temperature comes down accordingly. Contrary, in case the detected temperature is lower and the output voltage or current of the controller (1) becomes bigger, the opening degree of the electronic expansion valve (11) will become larger. As a result, the refrigerating capacity is decreased and the temperature goes up accordingly. At the time that the detected temperature becomes stabilized, the output voltage or current of the controller (1) is kept unchanged, and the opening degree of the electronic expansion device (11) is kept constant.

One end of the electronic expansion valve (11) is installed to a pipeline between the discharge outlet of the compressor (2) and a front end of the pressure regulating valve (4), and another end is installed on a pipeline between a location downstream from the throttling device (6) and the inlet of the evaporator (7). A thermal expansion valve is used to control the evaporating temperature and regulate degree of superheat independently. With the temperature close to the set value, the controller (1) will send a signal to control the electronic expansion valve (11) to release directly the hot vapor from the discharge outlet of the compressor (2) according to its opening setting. The pressure regulating valve (4) reduces the output of the refrigerating system by restricting the refrigerant entering the condenser (5), and thereby heating and refrigerating capacity is effectively controlled, and the temperature is precisely maintained at a set value. The electronic expansion valve (11) for the above mentioned hot-gas valve can be a type of continuously variable flow valve. A solenoid valve can also be used as hot-gas valve if cost reduction becomes more significant than the control precision of temperature and refrigerating capacity. 

What is claimed is:
 1. A refrigerating capacity control device comprising a refrigerating device, the refrigerating device including a compressor, an evaporator and a condenser, the compressor, the evaporator and the condenser being connected sequentially by pipelines; characterized by also comprising a controller, a pressure regulating valve, a throttling device, a control panel for driving a hot-gas valve and a hot-gas valve; the pressure regulating valve being located between a discharge outlet of the compressor of the refrigerating device and an inlet of the condenser; the throttling device being installed between an outlet of the condenser of the refrigerating device and an inlet of the evaporator; the hot-gas valve having one end installed on a pipeline between the discharge outlet of the compressor and a front end of the pressure regulating valve, and another end installed on a pipeline between a location downstream from the throttling device and the inlet of the evaporator; and the control panel for driving a hot-gas valve connecting the hot-gas valve to the controller.
 2. The refrigerating capacity control device according to claim 1, wherein the throttling device is a thermal expansion valve.
 3. The refrigerating capacity control device according to claim 1, wherein the throttling device is a capillary tube.
 4. The refrigerating capacity control device according to claim 1, wherein the throttling device is an electronic expansion valve.
 5. The refrigerating capacity control device according to claim 1, wherein the hot-gas valve is a continuously variable, electrically operated valve or an on/off solenoid valve.
 6. A testing apparatus incorporating the refrigerating capacity control device of claim 1, the testing apparatus comprising: a refrigerating capacity control device and a chamber or bath requiring temperature control; the refrigerating capacity control device comprising a refrigerating device which comprises a compressor, an evaporator and a condenser, the compressor, the evaporator and the condenser being connected sequentially by pipelines; the refrigerating capacity control device also comprising a controller, a pressure regulating valve, a throttling device, a control panel for driving a hot-gas valve and a hot-gas valve; the pressure regulating valve being located between a discharge outlet of the compressor of the refrigerating device and an inlet of the condenser; the throttling device being installed between an outlet of the condenser of the refrigerating device and an inlet of the evaporator; the hot-gas valve having one end installed on a pipeline between the discharge outlet of the compressor and a front end of the pressure regulating valve, and another end installed on a pipeline between a location downstream from the throttling device and the inlet of the evaporator; the control panel for driving a hot-gas valve connecting the hot-gas valve to the controller; the evaporator being installed in the chamber or bath requiring temperature control; a temperature sensor being installed in the chamber or bath requiring temperature control; and the temperature sensor being connected to the controller.
 7. A refrigerating capacity control method utilizing the testing apparatus of claim 6, characterized by comprising: installing a pressure regulating valve between the compressor and the condenser of a traditional refrigerating device; installing one end of a hot-gas valve on a pipeline between a discharge outlet of the compressor and a front end of the pressure regulating valve, and another end of the hot-gas valve on a pipeline between a location downstream from the throttling device and an inlet of the evaporator; connecting the hot-gas valve to the controller by using a control panel for driving a hot-gas valve; installing a throttling device between an outlet of the condenser of the refrigerating device and the inlet of the evaporator; wherein the pressure regulating valve is used to maintain a stable discharge pressure and a hot-gas temperature to avoid the discharge pressure being affected by switching-on or switching-off of the hot-gas valve; wherein the throttling device is used to control independently the evaporating temperature and degree of superheat; and wherein the hot-gas valve releases directly the hot vapor from the discharge outlet of the compressor according to its opening setting, the pressure regulating valve reduces the output of the refrigerating system by restricting the refrigerant entering the condenser, and thereby heating and refrigerating capacity is effectively controlled and the temperature is precisely maintained at a set value. 